Electric-boiler construction



Dc. 4 1923. F. T. KAELIN ELECTRIC BOIILER couswnucwxou Filed Jan. '5,1922 hire/7hr Patented lilac. 4, 1923.

. UNITED STATES T. KAELIN, OF MONTREAL, QUEBEC, CANADA.

ELESTHIG-BGILER CONSTRUCTION.

Application filed January 3, 1922. Serial No. 526,735.

This invention relates to improvements in the construction of boilers orvessels for use 1n the electric generation of steam or in other cases inwhich an electric-dischargev takes place within a vessel, and the objectof the invention is to provide a vessel so constructed as to escape orresist destruction by the action or passage of electric current.

Another object is to provide for the free circulation of liquid in sucha vessel and to avoid as largely as possible interference with liquidmovements in the vessel by elements therein, such as electrodes.

Still another object is to provide for operation of devices of thischaracter with a maximum of efiiciency and without danger to theapparatus.

Dealing, for the sake of explanation, with an electric boiler, it may bepointed out that the arrangement of electrodes within the boiler can besuch that the discharge is between electrodes and the shell of theboiler or between the electrodes themselves. Even if the discharge isintended to be only between electrodes, there is a certain amount ofdischarge-between the electrodes and the shell. If, therefore, the shellhas internal projections, the discharge will localize at these pointsand, on account of the frequent high current densities, the boiler is ingrave danger of being weakened by the current tearing away smallparticles of metal in a manner similar to that which obtains when an arcis formed. Such action is hereinafter referred to by the termelectrolysis which however must notbe confused with electrochemicalaction, commonly termed electrolytic action. This electrolysis isseemingly unavoidable and occurs when the shell of the boiler is notintended to be used as the ground electrode.

This invention aims primarily to provide a vessel of such constructionthat the shell thereof, which is subjected to mechanical stresses, willbe protected from weakening by electrolysis. This result is obtained inV conductor.

part by the construction of the vessel itself but largely by theprovision of a protective inner shell spaced from the outer and suitablygrounded and. designed to serve as an electrode.

In the drawings whichillustrate one em bod'iment of the invention Fig. 1is a vertical sectional view of a vessel designed to be used as a boilerfor the generation of steam by electric current.

Fig. 2 is a cross sectional view of the same.

Referring more particularly to the drawings, 11 designates an outercylindrical shell provided with lower and upper heads 12 and 13 of anysuitable form connected to the shell in any suitable way. The practicalconsiderations of boileiflm'aki-ng render it substantially impossible toproduce an inner surface free from projections without resorting tocostly methods of manufacture. According to this invention, theouter'shell is constructed in any desired way without regard to theinternal projections such as rivet heads, plate edges at seams and thelike.

which may result. The boiler is provided with an inner c lindrical shell14 disposed concentrically o the outer shell 11 and preferably of openended construction. This shell extends considerably above andbelow theelectrodes 15, so that no discharge will take place between theelectrodes and the outer shell owing to the interposition of the Yinner-shell. This inner shell is formed with a perfectly smooth innersurface and it will be readily understood that as the shell is notsubjected to mechanical stresses and is open ended that this result maybe easily accomplished by electric or otherwise welding a bent-up plateor by employing large diameter seamless tubing. This inner shell issupported in any suitable way, for example, by straps 16 and ispreferably provided with a grounding connection 17 com nected directlyto it so that reliance is not placed upon the outer shell as an electricThe electrodes may be of any suitable form and number. In the form shownthe electrodes-are three in number for connection to a. three phasecircuit but ends and suspended by a ground connection 19. llt will beunderstood that the inner shell 14 serves also as a ground electrodeand, owing to the greater surface which it presents to the electrodes 15as compared with the surface of the ground electrode 18, the electrodes15 are placed nearerto the electrode 18 than to the shell 14,-, in orderto approximately equalize resistances on the opposite sides of theelectrodes 15. This also serves in a measure to equalize steamgeneration on bcth sides of the electrodes 15 and to prolong the life ofthe electrodes.

In vessels. designed to contain liquids and where the level of theliquid changes -frequently, it has been found that there may be atendency to local changes of level. In order to overcome any tendency inthis direction due to'unequalevaporation of water on opposite sides ofthe electrode, but chiefly to permit circulation of water which in adevice of this character usually enters at the centre of the bottom, theelectrodes are, according to this invention, provided with slots 20disposed'parallel with the direction of current flow in the electrodes;These slots givecommunication between the annular spaces around andwithin the electrodes. If a central or grtuind electrode 18 is used, asshown in the drawings, it will be obvious that there is no Consumptionof water Within this electrode, whereas there is a considerable andconstant consumption outside. In order to keep the water levels insideand outside this electrode approximately constant, especially on accountof inflowing water entering the electrode 18, it may be provided withslots 21. As the current flow in such an element is not as clearlydefined as in the electrodes 15, the slots may be diposedcircumferentially as shown. This is especially advisable where more thanone electrode 15 is disposed in the vessel, since the current flow inthe ground electrode 18 is then in a substantially circumferential direction, from one electrode 15 to another, through the member 18.Obviously the inner shell 14: "should not be slotted as this wouldexpose the outer shell 11 to the dctructive electrolysis which it isparticularly desired to avoid.

VVhilethe invention has been described as applied to a steam boiler, itwill be understood that it is not limited to such use but pertains toall classes of vessels where it is desired to protect a shell undermechanical load from electrolysis.

Having thus described my invention what I claim is 1. In apparatus forheating liquids, a vessel having the walls thereof in contact with theliquid to be heated, means within the vessel for effectingelectricdischarge through the liquid to be heated, and a protectiveshell interposed between the vessel Latches walls and the electricdischarge means to prevent discharge between such means and the vesselwalls and to prevent mechanical weakenin of the walls b reason of an iher having the same polarity as the vessel,

whereby no electric discharge will occur between the vessel walls. andsaid member but electric discharge may occur between the electrode andsaid member.

3. In apparatus for electrically heating liquids, a grounded vesselhaving the walls thereof in contact with the liquid to be heated, meansfor effecting electric discharge through the liquid to be heated, and agrounded member interposed between such electric discharge means and theshell, whereby any electric discharge which would take place between thedischarge means and vessel with destructive effect on. the latter willtake place between thedischarge means and said member withoutdestructive. etlect upon the vessel walls.

4-. In apparatus for electrically heating liquids, a vessel having thewalls thereof subject to mechanical stress such as by in ternalpressure, electric discharge means-in such vessel, and a protectivemember not subject to mechanical stress interposed between the dischargemeans and the vessel walls and electrically connected with the vesselwalls, whereby any electric discharge between such discharge means andthe vessel will occur between the discharge means and protective member.

5. In apparatus for; electrically heating liquids, a vessel adapted tocontain such liquids and to Withstand mechanical stress such as byinternal pressure, electric heating means within the vessel, said vesselcomprising a mechanical stress resisting shell and a lining electricallyconnected to the vessel and interposed between the vessel proper and theelectric heating means, whereby any discharge between the vessel and theheating means will occur between said lining and the heating means andwill relieve the mechanically loaded portions of the vessel of electricstress and protect the same from any detrimental action due to suchdischarge.

6. lin apparatus for electrically heating liquids, a. vessel adapted tocontain the liquids and to resist mechanical stress, the said vesselhaving internal projections such as seams and rivets, electric heatingmeans disposed within the vessel and a shell interposed between theheating device and the vessel electricaily connected to the vesset andcovering the internal projections-thereof and presenting to the heatingdevice a smooth surface, whereby in the event of discharge between thevessel and heating device localizing of such discharge upon the internalprojections of the vessel proper will be prevented and uniform currentdensity will obtain at the surface of said protective shell.

7. In apparatus for heating liquids by passage of an electric currentthrough the liquid between the vessel containing the liquid and anelectrode within the vessel,

- means to prevent destruction or mechanical weakening of the vessel byreason of such discharge comprising a shell electrically connected tothe vessel and interposed between the vessel and the electrode, wherebythe discharge will occur between the electrode and said shell.

8. A device according to claim 7, in which the shell is under nomechanical load such as may obtain in the vessel proper.

9. Adevice according to claim 7, in which the shell is spaced from thevessel and covers any internal projections thereof such as seams andrivets.

10. A deviceaccording to claim 7, in which the shell comprises a smoothsurface disposed in such relation to the electrode as to obtain uniformcurrent density at the surface of such shell.

In witness whereof, I have hereunto set my hand.

FREDERICK T. KAELIN.

